1. Field of the Invention
The invention relates to a method and an apparatus for operating a drive device.
2. Description of the Prior Art
In the industry, a method and an apparatus for operating a drive device in the form of an engine cooling fan for the internal combustion engine of a motor vehicle are known. The engine cooling fan serves to subject an engine radiator to an air flow, and thus to cool down the coolant, heated by the engine and circulated between the engine and the radiator and dissipate heat of the combustion process from the engine into the environment.
Typically, the drive of the engine cooling fan in modern vehicles is done by a DC motor. To reduce the energy expenditure for this electric drive, its power is adapted to the combustion heat to be dissipated from the engine at the present time.
In the simplest case, this is done by switching on the engine cooling fan only as soon as the air flow, generated by the driving situation, is no longer adequate for engine cooling, and then it is operated at a fixed rpm, which ensures adequate engine cooling in all conceivable driving and environmental situations.
However, a control in which the power of the engine cooling fan is adapted continuously during travel operation to the actual cooling power required is more favorable in energy terms. The control unit of the engine cooling fan (fan control module, FCM) used for this purpose is capable of varying the rpm of the electric drive of the engine cooling fan over a wide rpm range, for instance from 0 to 3000 min−1. The target rpm ntarget required for the actual driving mode is then defined in the vehicle control unit (ECU) by the engine management system and transmitted as a PWM (pulse width modulation) signal to the engine cooling fan. The conversion of the rpm demand into an electrical voltage for driving the engine cooling fan then takes place in the control unit of the engine cooling fan.
The engine cooling fan is a noise source, and as such is taken into account in determining noise requirements at the vehicle level. In critical rpm ranges, because of resonance, the engine cooling fan may possibly generate an increased noise level on its own or in its surroundings. The electric drive of the engine fan can also cause vibration that matches the natural frequency of the engine cooling fan or its surroundings.
The object of the invention is to optimize the operating performance of the drive device, in particular with regard to the development of noise and other vibration.